Communication cable



A nl 2, 1968 K, R. BULLOCK COMMUNICATION CABLE Filed Aug. 2, 1965 FIG.1

SELF- BONDED POLYETHYLENE FIBROUS SHEET SELF BONDED POLYETHY LENE FIBROUS SHEET FIG. 2

CONDUCTOR ITW E m m T w m 2 3 w W I l. T .1 A .3 w R .0 s T N C U D m C m IT R A L Y. M n w mm ME ww I POLYETHYLENE JACKET Kenneth R. Bullock zg ywym ATTORNEYS 3 ,376,378 Patented Apr. 2, 1968 3,376,378 COMMUNICATIQN {TABLE Kenneth R. Bullock, Sycamore, ill, assignor to Anaconda Wire and 'Cable Company, New York, N.Y., a corporation of Delaware Filed Aug. 2, 1965, Ser. No. 476,328 3 Claims. (Cl. 174107) This invention relates to cables and, more particularly, to a new insulation covering for an electrical conductor of said cable. The invention is based on the discovery that when an electrical conductor is insulated by a sheet of self-bonded randomly distributed polyethylene fibers, the resultant cable made up of a plurality of these insulated conductors possesses desirable characteristics particularly suitable in telecommunication such as for telephone cables.

Broadly stated, the cable of this invention comprises at least one electrical conductor and an insulation covering thereon. The covering is a sheet of self-bonded continuous lengths of a substantially linear polyethylene fiber randomly distributed in multi-directional overlapping and intersecting arrangement through the sheet to provide a sheet density greater than about 7 lbs/ft. and a tensile strength above 0.3 lb./in.//oz./yd. Preferably, the fiber is less than above 4 microns in thickness.

The insulation covering for the present invention is made from linear polyethylene in the form of an integral network of primarily ribbon-like fibers which have cross sections varying along the length of the fibers. These fibers may be incorporated into the sheet structure in a direct laid-down process in which the fibers issuing from the spinnerette are spun directly onto a moving belt to form a loose sheet wherein the fibers are laid one on top of the other in overlapping multi-directional intersecting patterns. The loose sheet is then compacted by calendering to the desired thickness. The final product in sheet form is a material ranging from soft fabric-like to stronger paper-like sheets. It is chemical, moisture, oil, and grease resistant and has excellent dimensional stability. Its melting point is about 135 C. and remains flexible at temperatures as low as 116 C. Some properties of two typical sheets of self-bonded polyethylene fibers, one is paper-like and the other fabric-like material, are listed in Tables 1 and 2, as follows:

TABLE 1.PHYSICAL PROPERTIES PAPER-LIKE SHEET;

Basis Weight (Om/Yd!) 1. 5 2. Thickness (Mils) 4-5 p 6-8 Elmendorf Tear (Lbs. 0. 6/0. 6 0.8/0.8 Strip Tensile (Lbs/In. 33. 0/31. 0 47. 0/40. 0 Elongation (Percent) 17. 1/22. 3 18. 0/23. 0 MIT Flex (Cycles) 20M 20M TABLE 2.-PHYSICAL PROPERTIES FABRIC-LIKESHEET Basis Weight (Oz/YdJ), Nominal 1.5 Thickness (Mils) 5. 2 8. 8 Strip Tensile (Lbs/In.) 7. 6/7. 2 12. 0/11. 17. 0/43. 0

Elongation to Break (Percent) 25. 0/28. 0 27. 0/32. 0 31 0/43. 0 Grab Tensile (Lbs) 20. 0/18. 0 27. 0/26. 0 50. 0/40. 0 Tongue Tear (Lbs) 2. 7/2. 6 3.2/3.0 5. 5/5. 3

When electrical conductors insulated in accordance with the teaching of this invention are used in a communication'cable consisting of a plurality of pairs of insulated wires, the mutual capacitance is less than 0183v f/mile at 1000 c.p.s. for a sheet less than 4 mils in thickof self-bonded polyethylene fibers can be as low as 1.0 f

and the mutual capacitance less than 0.83 ,ef/mile at a thickness less than 1.4 mils.

In the manufacturing of insulated electrical wires in accordance with this invention, a single strip of paperlike self-bonded polyethylene fibrous sheet is wrapped helically around the electrical conductor to serve as insulation. Alternatively, the strip of insulation may be applied around the conductor in a manner so as to provide a longitudinal wrap. In the latter method, we prefer to use a wire covering and tube forming die as disclosed in the copending application Ser. No. 383,335, filed July 17, 1964, by Harvey Burr, and assigned to the same assignee as the present invention, to manufacture insulated electrical wires. The resultant insulated Wires are then used to make up a standard communication cable.

Further to illustrate this invention, a specific example is described hereinbelow with reference to the accompanying drawings wherein FIG. 1 is an isometric view of a fragmentary strip of self-bonded polyethylene fibrous sheet,

FIG. 2 is a side view partially in section of an insulated electrical wire,

FIG. 3 is an enlarged cross section through line 44 of FIG. 2, and

FIG. 4 is a side viewof a communication cable of this invention with layers partially removed to show its construction. i

Referring to the drawings, the insulation sheet 10 of FIG. 1 is a paper-like product made of linear polyethylene fibers. It has a nominal thickness of 3 to 4 mils and a basis weight of 1.0 oz./yd. In FIG. 2, the sheet 10 is pre-slit to in. tape and is applied on a 19 AWG copper wire 11 with left-hand lay 15 to 20 wraps per foot to form an insulation 12 which has a cross section as shown in FIG. 3. The insulated wires 12 are used for manufacturing telephone cable.

With reference to FIG. 4, the insulated wires 12 are first twisted i-nto pairs 13. 26 pairs then form the core 14. The twining is right-hand lay with a lay length of 2.7 to 5.5 inches. The core is covered with a GRS-Mylar tape 15. A noncorrugated aluminum shield 16 and a corrugated steel shield 17, flooded with a corrosion resistant compound, are in turn placed over the cover 15. A low density polyethylene jacket 18 is then extruded over the corrugated steel shield 17 to form a standard Stalpeth cable 19. The finished Stalpeth cable 19 and the insulated wire 12 are subject to routine mill tests using standard test procedures. The electrical measurements of the cable and the wire were also made using standard measurement procedures as follows:

Primary and secondary parameters at carrier frequencies.

Physical make-up of core Far-end crosstalk coupling loss.

'- Dielectric strength Voltage applied from each conductor to all other conductors and shield grounded on IO-foot sample.

Dielectric constant of the spun bonded material was determined from measurements of coaxial capacitance and 3 dimensions on a 30-ft. single conductor, 19 AWG with selfbonded polyethylene tape applied helically, by hand, and covered with an aluminum backed shield.

For the purpose of comparison, a standard Stalpeth, 26 pair, 19 AWG telephone cable containing paper insulated electrical conductors was similarly tested. The results of these tests and the physical make-up are shown in the following Tables 3 to 7:

TABLE 3.PHYSICAL MAKEUP OF CABLES AS DETER.

MINED FROM ELECTRICAL AND PHYSICAL MEASURE MENTS ON FINISHED SAMPLES Self-Bonded Paper Polyethylene Insulated Wire Diameter:

Wire Insulation:

-0. Zia Thickness, mils -3 4 Inter Axial Spacing:

Min., milsm- 54. 66 56. 4 Avg., mils- 56. 09 58.06 Max., mils 58. 15 59. 88

Pair Space:

' Min., KCM 9. 97 10.68 Avg., KCM 10.54 11. 30 Max., KC 11. 32 12. 01

Core Diameter, in. 0. 523 0. 542

Diameter under Shield over GRS tape, in 0.627

Diameter under Shield over paper tape, in. 0. 610

Diameter over Shield, in 0.735 0. 727

Over-all Diameter, in 0. 811 0. 823

TABLE 4.-ELECTRICAL CHARACTERISTICS Poly Paper Spun Mutual Capacitance at 1,000 c.p.s. in L/Mi;

M .0708 0799 Avg 0750 0825 M 0793 0865 Stand. Dev 00195 .00172 Reference Transverse Devlation 2.60 2. 08 Loop Resistance in Ohms/Mi.:

Min 83.16 83.70 Avg 84. 57 Max 85. 65 Stand. Dev .508 Dielectric Constant:

Material 1. 54 1. 8-2. 6 Avg. Effective 1. 1.58 Far-End Crosstalk at 150 KcJS. Db/1,000 Ft;

Avg Capacitance Unbalance at 1,000 c.p.s. in Pf/Length:

Pair-Pair:

ms Stand. Dev..

TABLE 5-PRIMARY AlgD SECONDARY PARAMETERS FROM RID GE READINGS FREQ=Frequency, cycles per second R: Resistance, Ohms per mile at 68 F. L=Inductance, Millihenries per mile G= Conductance, Micromhos per mile C=Capacitance, Microfareds per mile ZOM=Characteristic impedance, magnitude in Ohms ZOA=Charaeteristic impedance, angle in degrees A=Attenuation, DB per mile B=Phase constant, radians per mile VEL=Ve1ocity of propagation, miles/sec.

[26 PR 19 AWG Stalpeth self-bonded pcplyetlsiyilene cable. 26 pairs of 30.0 it. at 760 F., o e 1 F REQ R L Cr C Z OM Z 0A A B VE L TABLE 6.-PRIMARY AND slggNDARY PARAMETERS FROM BRIDGE DINGS [26 PR 19 AWG Stalpeth soit paper insulated cable 26 pairs oi 30.0 it. at 75.0" F'.]

FREQ, R L G C ZOM ZOA A B VEL 6 TABLE 7 -RESULTS OF MILL TESTS FOR SELEBONDED a substantial longitudinal overlap around the Wire so POLYETHYLENE STALPETH CABLE as to avoid a bare spot during the subsequent bending Test Result Spec. and twining operations. Using the die disclosed by Burrs copending application as previously identified, the infifig Shield OK 5 sulation sheet can provide about 2 wraps around the con- High Voltage 0-0. High Voltage C-G Shield Resistance 500V.Af., zsec. ductor in a continuous process in which an advancing i gggx g g z h conductor is longitudinally wrapped with the insulation Insulation Resistance 20,7001... 1,000 meg. min. sheet. The self-bonded polyethylene fibrous sheet is par- Mltual Capacl' 0-0760 ticularly advantageous for use in Burrs die because of 10 its substantially uniform thickness, high tensile strength, The test results indicate that the average efiect of the and Inherent p e P PP For e p the n dielectric constant of the finished cable with the self- Peratllfe of the the, Whleh must hlgh When P p bonded polyethylene fibrous insulation is about 81.6% sulation is used for melding the insulation to the nominal value occurring in a cable with paper insulation duetor, ean he suhstentlally l for t Polyethylene and exhibits a negligible variation over the frequency sheet and the resultant lhsulatleh Wlre helng the P y range from 1 kc./ s. to 1 mc./s. The conductance characene sheet'has less tendeneyte W p at Its g nd to open teristic of this new insulation covering is considerably when 1t 15 The p s q y f PP whleh better than that of paper insulated cables. The better conf out from the can be lnnnedlately tWlSted lnte ductance characteristic leads to lower attenuation at car- P rier frequencies. We found that the strength of the self- I 9131111: bonded ethylene tape is adequate since no breaks occur A eommunleatlen Cable eelnpl'lslng e p f y of during manufacture and no Shiners were evident in the pairs of insulated wires, at least one metallic shield profi i h d sample tectin-g said wires and an outer resir 1ous plastiojacket The lower relative dielectric constant of the self-bonded covetl'ng Sa1d Shield, h 9f aul Wires compris ng an polyethylene tape, as compared to that of paper, permits electrical conductor and an 1nsulat1o n hav ng a thickness an estimated reduction in insulation thickness of 20% of 3 to 4 H1115 thereon, sald covel'mg 136mg 3 sheet 113 to respectively, for 19 and 24 AWG cables from the web f P selfebended C HlZiIIUOHs lengths of a subaper thi k presently 1 The corresponding stantially linear polyethylene fiber 1n mult1-d1rect1onal reductions by Weight due to lower density of the selfeverlappms e lhtetactlhg arfangement throughout Sflld bonded polyethylene material are above 65% and 66%, 30 Sheet Provldmg Sheet denslty greater h about 7 respectively. This, in turn, results in a decrease of 13% to lbsfft. and a tensile strength above 0.3 lb./in.//oz./yd. 15% in over-all diameter in all pair counts as shown in a d1e1 ectr1e Constant less than aheut and a mutual T bl 8; capacitance less than 0.83 ,uf./rn1le at 1000 c.p.s. for a sheet 3 to 4 mils in thickness, and said fiber being less TABLE 8.COMPARISON 0F REQUIREMENTS FOR CABLES WITH SPUNBONDED POLYE'IHYLENE AND PAPER than about 4Inlel'ens 1n thickness- IIEISULATION TO ACHIEVE A MU CAPACITANCE 2. A communication cable as in claim 1 wherein said 0 M83 f/mfle sheet is helically wound on said conductor providing I sulat on said insulation covering. AWG Paper SBPE Percent 3. A communication cable as in claim 1 wherein said Reduction 40 sheet is longitudinally wrapped around said conductor pro- 19 Thickness, l 3 5 2 8 2O said ins latiOn C vering- 24 fi lqkonduetonlb./1000ft 51312 232 Wt. fC ii( 1 1ietor, lb ]l0(l6 it: II 01162 01055 00 References cued Core Diametermches UNITED STATES PATENTS Pair Count Paper SBPE Percent 2,589,700 3/1952 Johnstone 174106 Reduction 2,952,728 9/1960 Yokose 174120 X 19 25 M M76 136 3,077,510 2/1963 Olds 174120 X 100 1.110 .95 3,186,897 6/1965 Hochberg 161-150 2. a ta a:

""" 100 I620 I630 1415 50 FOREIGN PATENTS 400 574,562 4/1959 Canada.

932,482 7/1963 Great Britain. While the above example uses a helically wound in- 993,920 6/1965 Great Bfltainsulation on the conductor similar results are obtained when the cable is insulated with a longitudinally wrapped DARRELL CLAY, Exammer' insulation. This type of insulation has its edge extending H, HUBERF-ELD, A, T. GRIMLEY, substantially parallel to the conductor. Preferably, it has Assistant Examiners. 

1. A COMMUNICATION CABLE COMPRISING A PLURALITY OF PAIRS OF INSULATED WIRES, AT LEAST ONE METALLIC SHIELD PROTECTING SAID WIRES AND AN OUTER RESINOUS PLASTIC JACKET COVERING SAID SHIELD, EACH OF SAID WIRES COMPRISING AN ELECTRICAL CONDUCTOR AND AN INSULATION HAVING A THICKNESS OF 3 TO 4 MILS THEREON, SAID COVERING BEING A SHEET IN WEB FORM OF SELF-BONDED CONTINUOUS LENGTHS OF A SUBSTANTIALLY LINEAR POLYETHYLENE FIBER IN MULTI-DIRECTIONAL OVERLAPPING AND INTERACTING ARRANGEMENT THROUGHOUT SAID SHEET PROVIDING A SHEET DENSITY GREATER THAN ABOUT 7 LBS./FT.3 AND A TENSILE STRENGTH ABOVE 0.3LB./IN.//OZ./YD.2, A DIELECTRIC CONSTANT LESS THAN ABOUT 2.0 AND A MUTUAL CAPACITANCE LESS THAN 0.83 UF./MILE AT 1000 C.P.S. FOR A SHEET 3 TO 4 MILS IN THICKNESS, AND SAID FIBER BEING LESS THAN ABOUT 4 MICRONS IN THICKNESS. 